1. Field of the Invention
The invention pertains to a geogrid comprising drawn, polymeric longitudinal straps which run parallel or substantially parallel to each other and polymeric transverse straps bonded to the longitudinal straps.
2. Description of the Related Art
Grids as such are known. In GB 2266540 a grid is described which is made of fully stretched polymeric longitudinal and transverse straps bonded together by means of, e.g., partial fusion of the straps.
WO 94/26503 describes a grid of drawn, polymeric straps bonded together by melting the polymer in the area of contact between the longitudinal and the transverse straps. The melting of the polymer is accomplished by heating conductive particles situated directly underneath the surface of the straps in a high-frequency electromagnetic field. In this way it is ensured that only the portion of the polymer used to effect the bond will melt. The remaining polymer is hardly affected at all and so the strength of the drawn straps remains substantially unaffected. The grid according to WO 94/26503 can, in principle, be subjected to heavy loads.
However, in actual practice it was found that in the case of heavy loads, e.g., such as occur in civil engineering structures (i.e., structures to do with, int. al., hydraulic and road engineering), loaded longitudinal straps will break at a significantly lower load and exhibit a significantly wider breaking load distribution than might be expected on the basis of the specifications of these straps and the bonding technique applied.